Standoff Detection of Explosives at 1 m using Laser Induced Breakdown Spectroscopy

Abstract

We report the 'standoff detection' of explosives at 1 m in laboratory conditions, for the first time in India, using Laser Induced Breakdown Spectroscopy combined with multivariate analysis. The spectra of a set of five secondary explosives were recorded at a distance of 1 m from the focusing as well as collection optics. The plasma characteristics viz., plasma temperature and electron density were estimated from Boltzmann statistics and Stark broadening respectively. Plasma temperature was estimated to be of the order of (10.9 ± 2.1) ×10 3 K and electron density of (3.9 ± 0.5) ×1016 cm -3 . Using a ratiometric approach, C/H and H/O ratios showed a good correlation with the actual stoichiometric ratios and a partial identification success could be achieved. Finally employing principle component analysis, an excellent classification could be attained.

Femtosecond Filaments for Standoff Detection of Explosives

“…The availability of commercialised and miniaturised nanosecond (ns) lasers has led to compact man-portable 16 , handheld LIBS systems and as well as field-deployable standoff systems 17 for the investigation of various samples of interest. Nanosecond laser systems have been widely used to carry out LIBS experiments to investigate organic materials and correlate their molecular structure, especially for explosives, in order to identify them [18][19][20] . Since LIBS spectra (unlike the Raman spectra) are not the fingerprints of an organic explosives (containing C, H, N, O) several chemometric techniques have been used in tandem to classify the explosives 21 .…”

Femtosecond laser induced breakdown spectroscopy based standoff detection of explosives and discrimination using principal component analysis

“…Laser induced breakdown spectroscopy has been extensively used in various fields owing to it's robust in situ elemental analysis, such as space exploration, pharmaceutical, soil and nutrient analysis and identification/discrimination of explosives [10][11][12][13][14][15][16][17][18]. To this end, nanosecond (ns) LIBS has been extensively used in analysing aerosols [19], process control and monitoring in metallurgical industry [20], planetary missions and detection of explosive residues [21][22][23][24] [29][30][31][32]. ST-LIBS spectra of a few explosive residues were recorded from 30 m distance, which were kept behind the transparent barriers such as PMMA and colourless glasses [33].…”